Idiopathic Scoliosis is a spine deformity of unknown cause generally defined as a lateral curvature greater than 10 degrees accompanied by a vertebral rotation 1. Adolescent Idiopathic Scoliosis (AIS) is one of the most frequent childhood deformities worldwide, characterized by a 3D spinal deformity with unknown cause, and represents both an immediate medical challenge and a chronic condition affecting individuals throughout their lives. It is the most common orthopedic condition requiring surgery in adolescents and affects 4% of this population. This condition is most commonly diagnosed between the ages of 9 to 13 years 2,3,4. The diagnosis is primarily of exclusion and is made only after ruling out other causes of spinal deformity such as vertebral malformation, neuromuscular or syndromic disorders. Traditionally, the trunkal asymmetry is revealed by Adams forward bending test and measured with scoliometer during physical examination. The diagnosis can then be confirmed by radiographic observation of the curve and the angle measurement using the Cobb method.
Once diagnosed, the primary concern for physicians in managing scoliotic children is whether the curve will progress. Indeed, the curve progression is often unpredictable and is more frequently observed among girls than in boys. If untreated, the curve can progress dramatically, creating significant physical deformity and even cardiopulmonary problems. These manifestations become life threatening when the curve exceeds 70 degrees. The current treatment options to prevent or stop curve progression include bracing and surgery. In general, bracing is recommended for curves between 25 and 40 degrees, while surgery is reserved for curve greater than 45 degrees or curves that are unresponsive to bracing. Today in the United States there are approximately one million children between ages 10 and 16 with some degree of IS. Approximately, 10% of children diagnosed with idiopathic scoliosis have curve progression requiring corrective surgery. About 29,000 scoliosis surgeries are done every year in North America, resulting in significant psychological and physical morbidity. (Goldberg M S, Mayo N E, Poitras B et al. The Ste-Justine Adolescent Idiopathic Scoliosis Cohort Study. Part I: Description of the study. Spine 1994; 19:1551-61; Poitras B, Mayo N E, Goldberg M S et al. The Ste-Justine Adolescent Idiopathic Scoliosis Cohort Study. Part IV: Surgical correction and back pain. Spine 1994; 19:1582-8).
Currently, there is no proven method or test available to identify subjects at risk of developing IS to predict which affected individuals require treatment to prevent or stop progression of the disease so that appropriate treatment can be early provided and prevent surgical complications and cardiac and/or respiratory problems. (Weinstein S L, Dolan L A, Cheng J C et al. Adolescent idiopathic scoliosis. Lancet 2008; 371:1527-37).
Therefore, the application of current treatments, such as bracing or surgical correction, is delayed until a significant deformity is detected or until a significant progression is clearly demonstrated, resulting in a delayed, less than optimal treatment and often important psychological sequels (Society S R. Morbidity & Mortality Committee annual Report 1997).
Currently, in order to detect the deformity, diagnosed children are subjected to multiple radiographs over several years, usually until they reach skeletal maturity. It is estimated that the typical patients with scoliosis wil have approximately 22 radiological examinations over a 3-year period. There are potential risks in multiple radiographic examinations. For this reason also, alternative approaches that could allow performing the prognosis of idiopathic scoliosis are strongly desirable.
The major limitation in developing prognostic tests that could facilitate treatment choices for patients is the heterogeneous nature of AIS. At the clinical level, the heterogeneity of AIS is clearly illustrated by the variability of curve patterns, localisations and curve magnitude even in families with multiple affected members.
In absence of reliable AIS phenotypes, there is a need to understand better the molecular changes associated with disease onset and spinal deformity progression. Molecular definition of disease is rapidly replacing traditional pathology-based disease descriptions in part because of its utility in identifying the optimal treatment regimen for patients.
To this effect, the existence of a differential melatonin signaling dysfunction was reported among AIS patients leading to their stratification into three functional groups or biological endophenotypes (Moreau et al., 2004); (Azeddine et al., 2007); (Letelier et al., 2008) and WO2003/073102 to Moreau. More particularly, AIS patients were stratified into three functional groups (FG1, FG2 and FG3) representing distinct biological endophenotypes. According to this stratification, the scoliotic patients and children more at risk of developing scoliosis are less responsive to Gi protein stimulation when compared with healthy control subjects, and the stratification is based on the percentage of degree of reduction relative to control group. The classification ranges were fixed between 10 and 40% for FG3, 40 and 60% for FG2 and 60 and 90% for FG1.
More recently, using the cellular dielectric spectrometry (CDS) technique, which is a label-free method for the functional evaluation of G proteins and endogenous receptors coupled to those proteins (Verdonk et al., 2006), it was found that the cellular response following melatonin receptor stimulation by melatonin was mainly Gi-dependent in normal osteoblasts and was reduced to different extents in osteoblasts derived from AIS patients (Akoume et al., 2010). Approximately 33% of asymptomatic children diagnosed with a defective Gi protein function have developed scoliosis many years later (Akoume et al., 2010).
Early detection/prognosis of scoliosis is not only critical to successful and less invasive clinical outcomes but broadens the range of treatment options for clinicians. Indeed, improving patients' stratification and disease staging represent key steps to select AIS patients for minimally invasive surgeries before their spinal deformity is too advanced. OPN, a multifunctional cytokine, has been identified as a potentially key pathophysiologic contributor in the development of idiopathic scoliosis. Particularly, increased plasma OPN levels in patients with idiopathic scoliosis and in bipedal mice, a well-established animal model of this disease, were correlated with the disease (see WO 2008/119170 to Moreau).
It is commonly accepted that the development of scoliosis is influenced by a postural mechanism. The bipedal condition, naturally present in humans or experimentally induced in animals seems to play an important role in the manifestation of scoliotic deformities (Machida et al., 1999). Importantly, it has been reported that mice on a C57BI/6 or C3HHe background develop scoliosis closely similar to human idiopathic scoliosis when they gain bipedal posture for 40 weeks following amputation of their forelimbs and tails (Machida et al., 2006); (Oyama et al., 2006).
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.